Staff at Windsor Castle, one of Britain's most popular tourists sites, begin voting today whether to go on strike over low wages. It is the first time Queen Elizabeth is facing such an action by members of the royal household.

The union representing 120 employees at Windsor Castle — everything from wardens to ticket officer personnel — will ballot members to decide whether to take action.

At the heart of the issue is whether workers should be expected to carry out extra duties, such as giving tours and acting as interpreters for visitors, at no extra pay, according to the BBC.

The head of the Public and Commercial Services Union, Mark Serwotka, says, "It is scandalous that staff are so appallingly paid and expected to do work for free that brings in money for the royal family. Workers at Windsor Castle are paid less than the living wage of roughly $12 an hour, and that new employee can start at just over $20,000 a year."

The union says it has proposed non-strike action that would involve "the withdrawal of goodwill," such as giving tours of the castle to paying visitors, The Guardian reports.

The newspaper says the Royal Collection Trust, a charity responsible for Queen Elizabeth's official residencies said employees could volunteer to give tours but they are not compelled to do so.

The trust says that revenues from sales and admissions were used for the care and conservation of the royal art collection and did not go to members of the royal family, according to Reuters.

Windsor Castle is the world's largest and oldest occupied castle, and attracts more than a million visitors a year, reports The Telegraph.

The staff balloting is due to be completed by mid-April. If they vote yes, a strike could commence just ahead of the U.K.'s general election.